1. Field of the Invention
The invention relates to self-passivating Cu laser fuses in an integrated circuit or semiconductor device prepared by using Cu-alloys and annealing steps to provide Cu/low k integration schemes. These self-passivating Cu materials may also be used in Cu-to-Cu wire bonding.
2. Description of Related Art
In the art of laser fuses used as a portion of a semiconductor, the state of the art is to use fuses of pure Cu; however, under this usage the fuses are very sensitive to corrosion and oxidation as soon as the fuse is blown and the Cu is exposed to the atmosphere.
Nevertheless, in Cu-oxide integration schemes it is possible to get around the aforementioned problem by innovative layout and design of the fuse (i.e. ending the fuse on top of W-bars and containing the Cu oxidation and corrosion in the Cu-features of the fuse).
This innovative layout and design approach is not feasible in Cu/low k metallizations because of the high diffusivity of moisture and oxygen in the typical low k field, for the reason that corrosion of the Cu fuse would proceed to adjacent Cu wirings due to poor liner integrity at the sidewalls of damascene features.
An alternative to the state of art approach in lieu of using pure Cu (which is very sensitive to corrosion plus oxidation as soon as the fuse is blown and Cu is exposed to the atmosphere), is the use of Al-fuses on top of a Cu-metallization. However, this alternative approach is expensive because it requires many additional steps in the manufacturing process.
U.S. Pat. No. 5,747,868 disclose a laser fusible link structure for semiconductor devices comprising: a plurality of laser fusible links, each fusible link having a link length extending along a length direction and a link width extending along a width direction; a first dielectric layer conformally covering the laser fusible links; for each laser fusible link, an etch mask member disposed on the first dielectric layer vertically aligned over its respective laser fusible link, each etch mask member having a mask length extending in the length direction and a mask width extending in the width direction, the mask width being greater than or equal to the link width of its respective fusible link and less than or equal to the minimum spot size of the laser; and the etch mask members extending beyond the window perimeter in the length direction, the window perimeter extending beyond the etch mask members in the width direction.
A laser fuse structure formed over an active circuitry of an integrated circuit is disclosed in U.S. Pat. No. 5,986,319. The integrated circuit comprises: active circuitry; a first insulating layer, the first insulating layer overlying the active circuitry; a metal fuse layer above the first insulating layer, the metal fuse layer including at least one fuse, the at least one fuse being a radiant-energy configurable fuse having a location such that the beam area of the radiant energy used to configure the at least one fuse overlaps the active circuitry; a first multi-metal protective layer underneath the at least one fuse, the first multi-metal protective layer sufficiently large to shield the active circuitry from the radiant energy not directly impinging upon the at least one fuse; a second insulating layer between the first multi-metal protective layer, and the at least one fuse; a second multi-metal protective layer underneath the first multi-metal protective layer, the first and second multi-metal protective layers being sufficiently large to shield the active circuitry from the radiant energy not directly impinging on the at least one fuse; and a third insulating layer on the second multi-metal protective layer, the third insulating layer disposed between the first and second multi-metal protective layer.
U.S. Pat. No. 5,622,608 disclose a process for preparing an oxidation resistant, electrically conductive Cu layer on a substrate, and subsequently annealing. The annealing step is believed to provide a metal oxide layer at the surface of the Cu layer upon annealing.
Passivated Cu conductive layers for microelectronic applications is disclosed in U.S. Pat. No. 6,057,223, in which the Cu conductors formed are included as a component in a microelectronic device. The conductor is formed by forming a metal layer on the surface of a microelectronic substrate, forming a Cu layer on the metal layer, and annealing the metal and Cu layers. The annealing step is believed to diffuse some of the metal layer through the Cu layer to the surface where the diffused metal forms a protective metal oxide at the surEace of the Cu layer. As a result, the metal oxide layer passivates the Cu layer.
In the semiconductor manufacturing art in which a laser fuse is made a portion of the semiconductor as an effective way to alter the operation of semiconductor devices after the device has been fabricated to provide implementing redundancy schemes to replace defective portions of an integrated circuit with redundant portions, there is a need in the case of Cu laser fuses to prevent corrosion and oxidation as soon as the fuse is blown by laser energy and the Cu is exposed to the atmosphere.
One object of the present invention is to provide a semiconductor device with a laser fuse portion comprising copper, in which the copper is not susceptible to corrosion as soon as the fuse is blown during energizing by a laser.
Another object of the present invention is to provide a semiconductor device with a laser fuse portion comprising copper, in which the copper is not subject to oxidation as soon as the fuse is blown by laser energy and the copper is exposed to the atmosphere.
A further object of the present invention is to provide a semiconductor device with a laser fuse portion comprising copper without the need of ending the fuse on top of W-bars to contain Cu oxidation and corrosion in the Cu-features, when the fuse is blown by laser energy and Cu is exposed to the atmosphere.
A still further object of the present invention is to provide a semiconductor device with a laser fuse portion that comprises Cu/low k metallizations in which corrosion of the Cu-fuse would normally proceed to adjacent Cu wirings (due to poor liner integrity at the sidewalls of damascene features) are made to resist corrosion and oxidation of the Cu-fuse upon subjection to laser energy.
In accordance with the invention, prevention of corrosion and oxidation of the Cu laser fuse portion of a semiconductor as soon as the fuse is blown by laser energy is avoided by passivating a Cu-alloy between the liner and a dielectric cap subsequent to an application of laser energy to break or blow the fuse, by an annealing step to provide a self-passivating dopant rich layer on top of the open Cu-laser fuse area and at the Cu-interfaces to surrounding metallic liners and dielectric diffusion barriers.